Plastic packaging (e.g. plastic bags, plastic packaging for ham, cheese, yoghurt, other foods and consumer products, and plastic utensils) and other plastic waste (e.g. bottle crates, garden furniture, buckets, plastic sledges, car bumpers, petrol cans, pipes, spools, computer shells, TV shells, plastic parts of fridges, etc.) are the most problematic and the fastest-growing type of waste. According to common solutions, this type of waste is primarily landfilled, burned or used as filler. These solutions pollute the environment, are expensive and waste material that could be used as a raw material for new products.
Aside from that, everyone knows about plastic-waste recycling solutions where the waste is first sorted, then cleaned, and plastics of the same type are recycled into a uniform mass, granules or new products. The process of recycling is type-based, which means that, for example, LDPE (plastic packaging and bags), HDPE (plastic bags and thick-walled plastic products) or PET (plastic bottles for beverages) waste is washed, crushed, dried and granulated. The plastics industry can use plastic granules made of one polymer as raw material for making new products. As sorting plastic waste by type is very expensive and time-consuming, mixed plastic waste that is not easy to sort is usually not recycled; it is either incinerated or landfilled.
As far as we know, there is no suitable solution for recycling polymers of different types. Compared to other materials, such as glass or metals, plastic polymers need to be processed longer to be recycled. The biggest problem is that polymers of different types do not mix because their molecular weight differs and they have long polymer chains. Heating polymers is not enough to break down their molecules. So, to be recycled, polymers often need to be identical to achieve effective mixing. If different types of plastic are melted together, according to known solutions they do not mix and form layers.
Such problems prevent the plastics industry from using unsorted mixed plastic waste, and sorting household and other plastic waste by types is very costly and almost impossible. The standard plastics industry that puts hundreds of millions of tons of plastic products on the market is set up to use ‘virgin’ or primary single-type plastic granules (LDPE, HDPE, PS, PP, PET, AB, composites (PS/PP, PP/PE, PS/PC) HIPS, EPS, PA, POM, PC, etc.), and its technological production solutions are not able to handle mixed or unclean plastic waste.
Various solutions attempting to recycle mixed plastic waste of different types are known from the state of the art of the recycling field. Such solutions, however, also involve sorting and/or the adding of other materials during the recycling process, to facilitate better binding of the mixture obtained by recycling.
E.g. the European patents EP0103754B1 (Dr. HERFELD GmbH & Co. KG) 28.05.1986, EP0620776B1 (Dr. HERFELD GmbH & Co. KG, Konrad Hornschuch Aktiengesellschaft) 15.01.1997, EP0800445B2 (Der Grune Punkt-Duales System Deutschland Aktiengesellschaft) 01.06.2005, describe solutions performing the recycling of plastic waste in a mixer or other similar device equipped with a rotating blade system, by crushing, heating until melting, compacting, and rapidly cooling the plastic waste. E.g. the U.S. Pat. No. 7,275,857 of the USA (Erema Engineering Recycling Maschinen Und Anlagen Gesellschaft M.B.H.) Feb. 10, 2007 describes a system of rotating blades for recycling mixed plastic waste, where a rotating disk located in the agglomeration chamber has blades attached to it at an angle, with their ends extending over the edge of the rotating disk towards the walls of the chamber.
The plastic waste compacting equipment of Costarelli (http://www.costarelli.com/index.php?option=com_oziogallery2&view=02flashgallery&Itemid=115&lang=en), Navarini (http://www.navarini.com/ML1400_e.htm), Cavagion (http://www.aaronequipment.com/usedequipment/plastics-equipment/densifiers/cavagion-45415001), Essegiemme (http://www.machinads.com/1496-essegiemme-agglomerator-500-kg-hr/details.html), and Reg-Mac (http://www.aaronequipment.com/usedequipment/plastics-equipment/densifiers/41203001), where plastic waste is crushed, heated, melted, and rapidly cooled with cold water, and the cooled-down plastic mixture is crushed, can be considered closest to the present solution. The blade system used by the equipment comprises a blade with two vanes mounted on a shaft. Such solutions are meant for processing non-rigid industrial or collected single-type plastics (e.g. PET, plastic film etc.). The plastic waste is taken to a granulating chamber, heated and melted, accompanied by mechanical processing to reduce its volume and remove moisture, obtaining spherical particles of irregular shape and size. The blade rotating at high speed initially cuts finely and gradually. The melting temperature is obtained due to mechanical friction. Adding cold water and using thermal shock achieves rapid aggregation, which is broken up by the blades at the same time.
Solutions known from the state of the art in the recycling field are only suitable for processing single-type identified plastic waste of low volume weight as the design of their blade systems causes the blades to wear out too quickly due to forces created in the course of processing mixed plastic waste of different volume weights, friction and high temperatures, or alternatively the equipment is too weak for making the blade system rotate at sufficient speed to achieve the melting temperature and crush the rapidly cooled-down plastic mixture again. Aside from that the solutions known from the state of the art of the recycling field cannot be used outdoors at temperatures below +5° C. The need to use warm insulated rooms makes recycling plastics complicated and expensive.
The known solutions require the preliminary washing of the plastic waste. This makes the plastic waste recycling process too energy intensive and environment polluting. The plastic waste must also be sorted preliminarily, and as only one type of non-rigid plastic waste can be processed at a time, the recycling productivity is extremely low, and recycling is time-consuming and energy intensive. When used indoors, the known solutions require the ventilation of the facilities and heating in winter. That also increases the energy consumption of the process. Water consumption for cooling during the final stage of the compacting process is too high. The blades of the known solutions are used to cut and must be sharpened up to once a day; aside from that the blades withstand less heat and melt, creating non-uniform fragments.
The shortcoming of the known solution is the weakness of the blade system design, which causes the blades to wear out quickly, fail to sufficiently crush the processed material, or break; these solutions do not enable the recycling of plastic waste in winter conditions, are too energy intensive, and pollute the environment. For these reasons, they do not allow the recycling of unidentified, unclean, and unsorted mixed plastic waste.